This invention relates to a method, system and product for modifying the dynamic range of encoded audio signals for compatibility with the dynamic range of a selected playback destination.
To more efficiently transmit digital audio data on low bandwidth data networks, or to store larger amounts of digital audio data in a small data space, various data compression or encoding systems and techniques have been developed. Many such encoded audio systems use as a main element in data reduction the concept of not transmitting, or otherwise not storing portions of the audio that might not be perceived by an end user. As a result, such systems are referred to as perceptually encoded or xe2x80x9clossyxe2x80x9d audio systems.
However, as a result of such data elimination, perceptually encoded audio systems are not considered xe2x80x9caudiophilexe2x80x9d quality, and suffer from processing limitations. To overcome such deficiencies, a method, system and product have been developed to encode digital audio signals in a loss-less fashion, which is more properly referred to as xe2x80x9ccomponent audioxe2x80x9d rather than perceptual encoding, since all portions or components of the digital audio signal are retained. Such a method, system, and product are described in detail in U.S. patent application Ser. No. 08/771,790 entitled xe2x80x9cMethod, System And Product For Lossless Encoding Of Digital Audio Dataxe2x80x9d, which was filed on the same date and assigned to the same assignee as the present application, and is hereby incorporated by reference.
Significantly, the dynamic range associated with either perceptually encoded audio or component audio is fairly large. In that regard, the dynamic range of most perceptually encoded audio systems is in the 120 dB range, quantized in 2 dB steps. The dynamic range of component audio systems may be as large as 256 dB, quantized in 1 dB steps.
Unfortunately, however, the dynamic ranges associated with many playback destinations where perceptually encoded audio or component audio are decoded and reassembled are often much smaller than the dynamic range of the encoded audio signal. Still further, no industry standards exist for audio levels in perceptually encoded audio. With the 120 dB dynamic range previously described, audio levels are xe2x80x9call over the place.xe2x80x9d
Thus, there exists a need for a method, system and product for modifying the dynamic range of audio signals encoded according to presently deployed perceptually encoded audio systems or component audio systems for compatibility with the dynamic range of a selected playback destination. Such a method, system and product would provide more consistent audio levels for a particular application without compromising the original source material, while using presently deployed encoded audio systems. In this fashion, such a method, system and product would make dialog, music, and sound effects in a movie, for instance, much more consistent so that a viewer need not repeatedly adjust volume control, and would also ensure that the dialog does not fall below the noise floor of a cable TV system.
Accordingly, it is the principle object of the present invention to provide a method, system and product for modifying the dynamic range of encoded audio signals for compatibility with the dynamic range of a selected playback destination.
According to the present invention, then, a method is provided for modifying a dynamic range of an encoded audio signal. The method comprises receiving the encoded audio signal, the encoded audio signal having a first set of scale factors associated with a first dynamic range, and identifying a playback destination for the encoded audio signal, the playback destination having a second dynamic range. The method further comprises mapping the first set of scale factors to a second set of scale factors associated with the second dynamic range, and replacing the first set of scale factors in the encoded audio signal with the second set of scale factors to create a modified encoded audio signal for decoding and reassembly at the playback destination.
A system for modifying a dynamic range of an encoded audio signal is also provided. The system comprises a receiver for receiving the encoded audio signal, the encoded audio signal having a first set of scale factors associated with a first dynamic range-, and means for identifying a playback destination for the encoded audio signal, the playback destination having a second dynamic range. The system further comprises control logic operative to map the first set of scale factors to a second set of scale factors associated with the second dynamic range, and replace the first set of scale factors in the encoded audio signal with the second set of scale factors to create a modified encoded audio signal for decoding and reassembly at the playback destination.
A product for modifying a dynamic range of an encoded audio signal is also provided. The product comprises a storage medium having computer readable programmed instructions recorded thereon. The instructions are operative to map a first set of scale factors associated with a first dynamic range of an encoded audio signal to a second set of scale factors associated with a second dynamic range of a playback destination, and replace the first set of scale factors in the encoded audio signal with the second set of scale factors to create a modified encoded audio signal for decoding and reassembly at the playback destination.